Validation of the PreOperative Score to predict Post-Operative Mortality (POSPOM) in Dutch non-cardiac surgery patients.

BACKGROUND: Standardized risk assessment tools can be used to identify patients at higher risk for postoperative complications and death. In this study, we validate the PreOperative Score to predict Post-Operative Mortality (POSPOM) for in-hospital mortality in a large cohort of non-cardiac surgery patients. In addition, the performance of POSPOM to predict postoperative complications was studied. METHODS: Data from the control cohort of the TRACE (routine posTsuRgical Anesthesia visit to improve patient outComE) study was analysed. POSPOM scores for each patient were calculated post-hoc. Observed in-hospital mortality was compared with predicted mortality according to POSPOM. Discrimination was assessed by receiver operating characteristic curves with C-statistics for in-hospital mortality and postoperative complications. To describe the performance of POSPOM sensitivity, specificity, negative predictive values, and positive predictive values were calculated. For in-hospital mortality, calibration was assessed by a calibration plot. RESULTS: In 2490 patients, the observed in-hospital mortality was 0.5%, compared to 1.3% as predicted by POSPOM. 27.1% of patients had at least one postoperative complication of which 22.4% had a major complication. For in-hospital mortality, POSPOM showed strong discrimination with a C-statistic of 0.86 (95% CI, 0.78-0.93). For the prediction of complications, the discrimination was poor to fair depending on the severity of the complication. The calibration plot showed poor calibration of POSPOM with an overestimation of in-hospital mortality. CONCLUSION: Despite the strong discriminatory performance, POSPOM showed poor calibration with an overestimation of in-hospital mortality. Performance of POSPOM for the prediction of any postoperative complication was poor but improved according to severity.

Epidemiology, Prehospital Characteristics and Outcomes of Severe Traumatic Brain Injury in The Netherlands: The BRAIN-PROTECT Study.

OBJECTIVE: A thorough understanding of the epidemiology, patient characteristics, trauma mechanisms, and current outcomes among patients with severe traumatic brain injury (TBI) is important as it may inform potential strategies to improve prehospital emergency care. The aim of this study is to describe the prehospital epidemiology, characteristics and outcome of (suspected) severe TBI in the Netherlands. METHODS: The BRAIN-PROTECT study is a prospective observational study on prehospital management of patients with severe TBI in the Netherlands. The study population comprised all consecutive patients with clinical suspicion of TBI and a prehospital GCS score ≤ 8, who were managed by one of the 4 Helicopter Emergency Medical Services (HEMS). Patients were followed-up in 9 trauma centers until 1 year after injury. Planned sub-analyses were performed for patients with "confirmed" and "isolated" TBI. RESULTS: Data from 2,589 patients, of whom 2,117 (81.8%) were transferred to a participating trauma center, were analyzed. The incidence rate of prehospitally suspected and confirmed severe TBI were 3.2 (95% CI: 3.1;3.4) and 2.7 (95% CI: 2.5;2.8) per 100,000 inhabitants per year, respectively. Median patient age was 46 years, 58.4% were involved in traffic crashes, of which 37.4% were bicycle related. 47.6% presented with an initial GCS of 3. The median time from HEMS dispatch to hospital arrival was 54 minutes. The overall 30-day mortality was 39.0% (95% CI: 36.8;41.2). CONCLUSION: This article summarizes the prehospital epidemiology, characteristics and outcome of severe TBI in the Netherlands, and highlights areas in which primary prevention and prehospital care can be improved.

The effects of preoperative moderate to severe anaemia on length of hospital stay: A propensity score-matched analysis in non-cardiac surgery patients.

BACKGROUND: Anaemia is frequently recorded during preoperative screening and has been suggested to affect outcomes after surgery negatively. OBJECTIVES: The objectives were to assess the frequency of moderate to severe anaemia and its association with length of hospital stay. DESIGN: Post hoc analysis of the international observational prospective 'Local ASsessment of VEntilatory management during General Anaesthesia for Surgery' (LAS VEGAS) study. PATIENTS AND SETTING: The current analysis included adult patients requiring general anaesthesia for non-cardiac surgery. Preoperative anaemia was defined as a haemoglobin concentration of 11 g dl-1 or lower, thus including moderate and severe anaemia according to World Health Organisation criteria. MAIN OUTCOME MEASURES: The primary outcome was length of hospital stay. Secondary outcomes included hospital mortality, intra-operative adverse events and postoperative pulmonary complications (PPCs). RESULTS: Haemoglobin concentrations were available for 8264 of 9864 patients. Preoperative moderate to severe anaemia was present in 7.7% of patients. Multivariable analysis showed that preoperative moderate to severe anaemia was associated with an increased length of hospital stay with a mean difference of 1.3 ((95% CI 0.8 to 1.8) days; P < .001). In the propensity-matched analysis, this association remained present, median 4.0 [IQR 1.0 to 5.0] vs. 2.0 [IQR 0.0 to 5.0] days, P = .001. Multivariable analysis showed an increased in-hospital mortality (OR 2.9 (95% CI 1.1 to 7.5); P  = .029), and higher incidences of intra-operative hypotension (36.3 vs. 25.3%; P < .001) and PPCs (17.1 vs. 10.5%; P = .001) in moderately to severely anaemic patients. However, this was not confirmed in the propensity score-matched analysis. CONCLUSIONS: In this international cohort of non-cardiac surgical patients, preoperative moderate to severe anaemia was associated with a longer duration of hospital stay but not increased intra-operative complications, PPCs or in-hospital mortality. TRIAL REGISTRATION: The LAS VEGAS study was registered at Clinicaltrials.gov, NCT01601223.

Anticoagulation management during pulmonary endarterectomy with cardiopulmonary bypass and deep hypothermic circulatory arrest.

INTRODUCTION: Pulmonary endarterectomy requires cardiopulmonary bypass and deep hypothermic circulatory arrest, which may prolong the activated clotting time. We investigated whether activated clotting time-guided anticoagulation under these circumstances suppresses hemostatic activation. METHODS: Individual heparin sensitivity was determined by the heparin dose-response test, and anticoagulation was monitored by the activated clotting time and heparin concentration. Perioperative hemostasis was evaluated by thromboelastometry, platelet aggregation, and several plasma coagulation markers. RESULTS: Eighteen patients were included in this study. During cooling, tube-based activated clotting time increased from 719 (95% confidence interval = 566-872 seconds) to 1,273 (95% confidence interval = 1,136-1,410 seconds; p < 0.01) and the cartridge-based activated clotting time increased from 693 (95% confidence interval = 590-796 seconds) to 883 (95% confidence interval = 806-960 seconds; p < 0.01), while thrombin-antithrombin showed an eightfold increase. The heparin concentration showed a slightly declining trend during cardiopulmonary bypass. After protamine administration (protamine-to-heparin bolus ratio of 0.82 (0.71-0.90)), more than half of the patients showed an intrinsically activated coagulation test and intrinsically activated coagulation test without heparin effect clotting time >240 seconds. Platelet aggregation through activation of the P2Y12 (adenosine diphosphate test) and thrombin receptor (thrombin receptor activating peptide-6 test) decreased (both -33%) and PF4 levels almost doubled (from 48 (95% confidence interval = 42-53 ng/mL) to 77 (95% confidence interval = 71-82 ng/mL); p < 0.01) between weaning from cardiopulmonary bypass and 3 minutes after protamine administration. CONCLUSION: This study shows a wide variation in individual heparin sensitivity in patients undergoing pulmonary endarterectomy with deep hypothermic circulatory arrest. Although activated clotting time-guided anticoagulation management may underestimate the level of anticoagulation and consequently result in a less profound inhibition of hemostatic activation, this study lacked power to detect adverse outcomes.

The vascular occlusion test using multispectral imaging: a validation study : The VASOIMAGE study.

Multispectral imaging (MSI) is a new, non-invasive method to continuously measure oxygenation and microcirculatory perfusion, but has limitedly been validated in healthy volunteers. The present study aimed to validate the potential of multispectral imaging in the detection of microcirculatory perfusion disturbances during a vascular occlusion test (VOT). Two consecutive VOT's were performed on healthy volunteers and tissue oxygenation was measured with MSI and near-infrared spectroscopy (NIRS). Correlations between the rate of desaturation, recovery and the hyperemic area under the curve (AUC) measured by MSI and NIRS were calculated. Fifty-eight volunteers were included. The MSI oxygenation curves showed identifiable components of the VOT, including a desaturation and recovery slope and hyperemic area under the curve, similar to those measured with NIRS. The correlation between the rate of desaturation measured by MSI and NIRS was moderate: r = 0.42 (p = 0.001) for the first and r = 0.41 (p = 0.002) for the second test. Our results suggest that non-contact multispectral imaging is able to measure changes in regional oxygenation and deoxygenation during a vascular occlusion test in healthy volunteers. When compared to measurements with NIRS, correlation of results was moderate to weak, most likely reflecting differences in physiology of the regions of interest and measurement technique.

Therapeutic interventions to restore microcirculatory perfusion following experimental hemorrhagic shock and fluid resuscitation: A systematic review.

OBJECTIVE: Microcirculatory perfusion disturbances following hemorrhagic shock and fluid resuscitation contribute to multiple organ dysfunction and mortality. Standard fluid resuscitation is insufficient to restore microcirculatory perfusion; however, additional therapies are lacking. We conducted a systematic search to provide an overview of potential non-fluid-based therapeutic interventions to restore microcirculatory perfusion following hemorrhagic shock. METHODS: A structured search of PubMed, EMBASE, and Cochrane Library was performed in March 2020. Animal studies needed to report at least one parameter of microcirculatory flow (perfusion, red blood cell velocity, functional capillary density). RESULTS: The search identified 1269 records of which 48 fulfilled all eligibility criteria. In total, 62 drugs were tested of which 29 were able to restore microcirculatory perfusion. Particularly, complement inhibitors (75% of drugs tested successfully restored blood flow), endothelial barrier modulators (100% successful), antioxidants (66% successful), drugs targeting cell metabolism (83% successful), and sex hormones (75% successful) restored microcirculatory perfusion. Other drugs consisted of attenuation of inflammation (100% not successful), vasoactive agents (68% not successful), and steroid hormones (75% not successful). CONCLUSION: Improving mitochondrial function, inhibition of complement inhibition, and reducing microvascular leakage via restoration of endothelial barrier function seem beneficial to restore microcirculatory perfusion following hemorrhagic shock and fluid resuscitation.

Women empowerment in anaesthesia research and clinical practice: meeting report from the British Journal of Anaesthesia Women in Anaesthesia Research symposium.

The Women in Anaesthesia Research Symposium (Prato, Italy; 4 June, 2019), supported by the British Journal of Anaesthesia in collaboration with Monash University, was organised to discuss challenges facing women in anaesthesia clinical practice and research. We provide an overview of institutional or departmental measures that were proposed during the symposium that may empower women in anaesthesia today.

Microvascular Alterations During Cardiac Surgery Using a Heparin or Phosphorylcholine-Coated Circuit.

OBJECTIVE: Heparin biocompatible coating frequently is used to reduce inflammation and blood coagulation during cardiopulmonary bypass (CPB) in cardiac surgery. Whether heparin coating is protective or damaging to the vascular endothelium is unclear. The authors investigated whether heparin-coated (HC) circuits are associated with better preservation of microcirculatory perfusion and glycocalyx dimensions compared with nonheparin phosphorylcholine-coated (PC) circuits. DESIGN: Prospective, randomized blinded study. SETTING: Tertiary university hospital. PARTICIPANTS: A total of 26 adults undergoing elective coronary artery bypass graft surgery with CPB. INTERVENTIONS: PC (n = 13) versus HC circuits (n = 13). MEASUREMENTS AND MAIN RESULTS: Sublingual microcirculatory perfusion was measured before, during, and after CPB using sidestream dark field imaging and analyzed for perfused vessel density and perfused boundary region, an inverse parameter for glycocalyx dimensions. Onset of CPB was associated with an increase in perfused boundary region in the PC group that continued until the third postoperative day (2.0 ± 0.2 to 2.5 ± 0.2 µm; p = 0.018). This was paralleled by increased plasma syndecan-1 levels in the PC group. Contrastingly, both parameters remained unaltered in the HC group compared with baseline levels. CPB decreased perfused vessel density in both groups (CPB v pre-CPB: PC: 17 ± 2 to 13 ± 2 mm/mm2, p = 0.006; HC: 16 ± 2 to 11 ± 2 mm/mm2, p = 0.003) and remained equally altered in the first 3 postoperative days. CONCLUSION: The use of an HC circuit is associated with better preservation of the endothelial glycocalyx compared with PC circuits, whereas microcirculatory perfusion was disturbed equally in both groups. Hence, CPB-induced microcirculatory perfusion disturbances seem to be coating independent.

Microcirculatory perfusion disturbances following cardiac surgery with cardiopulmonary bypass are associated with in vitro endothelial hyperpermeability and increased angiopoietin-2 levels.

BACKGROUND: Endothelial hyperpermeability following cardiopulmonary bypass (CPB) contributes to microcirculatory perfusion disturbances and postoperative complications after cardiac surgery. We investigated the postoperative course of renal and pulmonary endothelial barrier function and the association with microcirculatory perfusion and angiopoietin-2 levels in patients after CPB. METHODS: Clinical data, sublingual microcirculatory data, and plasma samples were collected from patients undergoing coronary artery bypass graft surgery with CPB (n = 17) before and at several time points up to 72 h after CPB. Renal and pulmonary microvascular endothelial cells were incubated with patient plasma, and in vitro endothelial barrier function was assessed using electric cell-substrate impedance sensing. Plasma levels of angiopoietin-1,-2, and soluble Tie2 were measured, and the association with in vitro endothelial barrier function and in vivo microcirculatory perfusion was determined. RESULTS: A plasma-induced reduction of renal and pulmonary endothelial barrier function was observed in all samples taken within the first three postoperative days (P < 0.001 for all time points vs. pre-CPB). Angiopoietin-2 and soluble Tie2 levels increased within 72 h after CPB (5.7 ± 4.4 vs. 1.7 ± 0.4 ng/ml, P < 0.0001; 16.3 ± 4.7 vs. 11.9 ± 1.9 ng/ml, P = 0.018, vs. pre-CPB), whereas angiopoietin-1 remained stable. Interestingly, reduced in vitro renal and pulmonary endothelial barrier moderately correlated with reduced in vivo microcirculatory perfusion after CPB (r = 0.47, P = 0.005; r = 0.79, P < 0.001). In addition, increased angiopoietin-2 levels moderately correlated with reduced in vitro renal and pulmonary endothelial barrier (r = - 0.46, P < 0.001; r = - 0.40, P = 0.005) and reduced in vivo microcirculatory perfusion (r = - 0.43, P = 0.01; r = - 0.41, P = 0.03). CONCLUSIONS: CPB is associated with an impairment of in vitro endothelial barrier function that continues in the first postoperative days and correlates with reduced postoperative microcirculatory perfusion and increased circulating angiopoietin-2 levels. These results suggest that angiopoietin-2 is a biomarker for postoperative endothelial hyperpermeability, which may contribute to delayed recovery of microcirculatory perfusion after CPB. TRIAL REGISTRATION: NTR4212 .

Society of Cardiovascular Anesthesiologists Clinical Practice Improvement Advisory for Management of Perioperative Bleeding and Hemostasis in Cardiac Surgery Patients.

Bleeding after cardiac surgery is a common and serious complication leading to transfusion of multiple blood products and resulting in increased morbidity and mortality. Despite the publication of numerous guidelines and consensus statements for patient blood management in cardiac surgery, research has revealed that adherence to these guidelines is poor, and as a result, a significant variability in patient transfusion practices among practitioners still remains. In addition, although utilization of point-of-care (POC) coagulation monitors and the use of novel therapeutic strategies for perioperative hemostasis, such as the use of coagulation factor concentrates, have increased significantly over the last decade, they are still not widely available in every institution. Therefore, despite continuous efforts, blood transfusion in cardiac surgery has only modestly declined over the last decade, remaining at ≥50% in high-risk patients. Given these limitations, and in response to new regulatory and legislature requirements, the Society of Cardiovascular Anesthesiologists (SCA) has formed the Blood Conservation in Cardiac Surgery Working Group to organize, summarize, and disseminate the available best-practice knowledge in patient blood management in cardiac surgery. The current publication includes the summary statements and algorithms designed by the working group, after collection and review of the existing guidelines, consensus statements, and recommendations for patient blood management practices in cardiac surgery patients. The overall goal is creating a dynamic resource of easily accessible educational material that will help to increase and improve compliance with the existing evidence-based best practices of patient blood management by cardiac surgery care teams.

Dutch Prospective Observational Study on Prehospital Treatment of Severe Traumatic Brain Injury: The BRAIN-PROTECT Study Protocol.

Background: Severe traumatic brain injury (TBI) is associated with a high mortality rate and those that survive commonly have permanent disability. While there is a broad consensus that appropriate prehospital treatment is crucial for a favorable neurological outcome, evidence to support currently applied treatment strategies is scarce. In particular, the relationship between prehospital treatments and patient outcomes is unclear. The BRAIN-PROTECT study therefore aims to identify prehospital treatment strategies associated with beneficial or detrimental outcomes. Here, we present the study protocol. Study Protocol: BRAIN-PROTECT is the acronym for BRAin INjury: Prehospital Registry of Outcome, Treatments and Epidemiology of Cerebral Trauma. It is a prospective observational study on the prehospital treatment of patients with suspected severe TBI in the Netherlands. Prehospital epidemiology, interventions, medication strategies, and nonmedical factors that may affect outcome are studied. Multivariable regression based modeling will be used to identify confounder-adjusted relationships between these factors and patient outcomes, including mortality at 30 days (primary outcome) or mortality and functional neurological outcome at 1 year (secondary outcomes). Patients in whom severe TBI is suspected during prehospital treatment (Glasgow Coma Scale score ≤ 8 in combination with a trauma mechanism or clinical findings suggestive of head injury) are identified by all four helicopter emergency medical services (HEMS) in the Netherlands. Patients are prospectively followed up in 9 participating trauma centers for up to one year. The manuscript reports in detail the objectives, setting, study design, patient inclusion, and data collection process. Ethical and juridical aspects, statistical considerations, as well as limitations of the study design are discussed. Discussion: Current prehospital treatment of patients with suspected severe TBI is based on marginal evidence, and optimal treatment is basically unknown. The BRAIN-PROTECT study provides an opportunity to evaluate and compare different treatment strategies with respect to patient outcomes. To our knowledge, this study project is the first large-scale prospective prehospital registry of patients with severe TBI that also collects long-term follow-up data and may provide the best available evidence at this time to give useful insights on how prehospital care can be improved.

Society of Cardiovascular Anesthesiologists Clinical Practice Improvement Advisory for Management of Perioperative Bleeding and Hemostasis in Cardiac Surgery Patients.

Bleeding after cardiac surgery is a common and serious complication leading to transfusion of multiple blood products and resulting in increased morbidity and mortality. Despite the publication of numerous guidelines and consensus statements for patient blood management in cardiac surgery, research has revealed that adherence to these guidelines is poor, and as a result, a significant variability in patient transfusion practices among practitioners still remains. In addition, although utilization of point of care coagulation monitors and the use of novel therapeutic strategies for perioperative hemostasis, such as the use of coagulation factor concentrates, has increased significantly over the last decade, they are still not widely available in every institution. Therefore, despite continuous efforts, blood transfusion in cardiac surgery has declined only modestly over the last decade, remaining at 50% or greater in high-risk patients. Given these limitations and in response to new regulatory and legislature requirements, the Society of Cardiovascular Anesthesiologists has formed the Blood Conservation in Cardiac Surgery Working Group in order to organize, summarize, and disseminate the available best-practice knowledge in patient blood management in cardiac surgery. The current publication includes the summary statements and algorithms designed by the working group, after collection and review of the existing guidelines, consensus statements, and recommendations for patient blood management practices in cardiac surgery patients. The overall goal is creating a dynamic resource of easily accessible educational material that will help to increase and improve compliance with the existing evidence-based best practices of patient blood management by cardiac surgery care teams.

Level of agreement of point-of-care and laboratory HbA1c measurements in the preoperative outpatient clinic in non-diabetic patients who are overweight or obese.

Implementation of point-of-care HbA1c devices in the preoperative outpatient clinic might facilitate the early diagnosis of glycemic disturbances in overweight or obese patients undergoing surgery, but validation studies in this setting do not exist. We determined the level of agreement between a point-of-care and laboratory HbA1c test in non-diabetic patients visiting the outpatient clinic for preoperative risk profiling. Point-of-care HbA1c levels were measured in whole blood obtained by a finger prick (Siemens DCA Vantage HbA1c analyzer) and in hemolysed EDTA blood in the central laboratory (LAB). Bland Altman and Clarke's error grid analysis were used to analyze the agreement between the point-of-care and laboratory measurements. Patients (n = 49) were 55 ± 11 years old, 47% were male with a body mass index (BMI) of 30.6 ± 3.4 kg/m2. The mean HbA1c was 38.1 ± 3.7 mmol/mol or 5.6 ± 0.3%. One patient was diagnosed with a HbA1c indicative for diabetes mellitus (6.7%). Bland Altman analysis revealed a bias of - 0.53 ± 1.81 mmol/mol with limits of agreement of - 4.09 to 3.03 mmol/mol and a bias of - 0.05 ± 0.17% with limits of agreement - 0.39 to 0.28%. The percentage error was 9.2% and 5.9% for HbA1c expressed in mmol/mol and %, respectively. Clarke's error grid analysis showed that 48 out of 49 measurements were located in area A (98%). Point-of-care HbA1c measurements showed a high level of agreement with the laboratory test in the outpatient setting, and may be used for preoperative risk profiling in patients prone to cardiometabolic complications.Trial registration: Netherlands Trial Register NTR3057.

Vasculotide, an Angiopoietin-1 Mimetic, Restores Microcirculatory Perfusion and Microvascular Leakage and Decreases Fluid Resuscitation Requirements in Hemorrhagic Shock.

BACKGROUND: Microcirculatory dysfunction is associated with multiple organ failure and unfavorable patient outcome. We investigated whether therapeutically targeting the endothelial angiopoietin/Tie2 system preserves microvascular integrity during hemorrhagic shock. METHODS: Rats were treated with the angiopoietin-1 mimetic vasculotide and subjected to hemorrhagic shock and fluid resuscitation. Microcirculatory perfusion and leakage were assessed with intravital microscopy (n = 7 per group) and Evans blue dye extravasation (n = 8 per group), respectively. The angiopoietin/Tie2 system was studied at protein and RNA level in plasma, kidneys, and lungs. RESULTS: Hemorrhagic shock significantly reduced continuously perfused capillaries (7 ± 2 vs. 11 ± 2) and increased nonperfused vessels (9 ± 3 vs. 5 ± 2) during hemorrhagic shock, which could not be restored by fluid resuscitation. Hemorrhagic shock increased circulating angiopoietin-2 and soluble Tie2 significantly, which associated with microcirculatory perfusion disturbances. Hemorrhagic shock significantly decreased Tie2 gene expression in kidneys and lungs and induced microvascular leakage in kidneys (19.7 ± 11.3 vs. 5.2 ± 3.0 µg/g) and lungs (16.1 ± 7.0 vs. 8.6 ± 2.7 µg/g). Vasculotide had no effect on hemodynamics and microcirculatory perfusion during hemorrhagic shock but restored microcirculatory perfusion during fluid resuscitation. Interestingly, vasculotide attenuated microvascular leakage in lungs (10.1 ± 3.3 µg/g) and significantly reduced the required amount of volume supplementation (1.3 ± 1.4 vs. 2.8 ± 1.5 ml). Furthermore, vasculotide posttreatment was also able to restore microcirculatory perfusion during fluid resuscitation. CONCLUSIONS: Targeting Tie2 restored microvascular leakage and microcirculatory perfusion and reduced fluid resuscitation requirements in an experimental model of hemorrhagic shock. Therefore, the angiopoietin/Tie2 system seems to be a promising target in restoring microvascular integrity and may reduce organ failure during hemorrhagic shock.

Correlation Coefficients: Appropriate Use and Interpretation.

Correlation in the broadest sense is a measure of an association between variables. In correlated data, the change in the magnitude of 1 variable is associated with a change in the magnitude of another variable, either in the same (positive correlation) or in the opposite (negative correlation) direction. Most often, the term correlation is used in the context of a linear relationship between 2 continuous variables and expressed as Pearson product-moment correlation. The Pearson correlation coefficient is typically used for jointly normally distributed data (data that follow a bivariate normal distribution). For nonnormally distributed continuous data, for ordinal data, or for data with relevant outliers, a Spearman rank correlation can be used as a measure of a monotonic association. Both correlation coefficients are scaled such that they range from -1 to +1, where 0 indicates that there is no linear or monotonic association, and the relationship gets stronger and ultimately approaches a straight line (Pearson correlation) or a constantly increasing or decreasing curve (Spearman correlation) as the coefficient approaches an absolute value of 1. Hypothesis tests and confidence intervals can be used to address the statistical significance of the results and to estimate the strength of the relationship in the population from which the data were sampled. The aim of this tutorial is to guide researchers and clinicians in the appropriate use and interpretation of correlation coefficients.

Prediction of Postoperative Blood Loss Using Thromboelastometry in Adult Cardiac Surgery: Cohort Study and Systematic Review.

OBJECTIVE: The aim was to evaluate the predictive value of thromboelastometry for postoperative blood loss in adult cardiac surgery with cardiopulmonary bypass. DESIGN: Retrospective cohort study and systematic review of the literature. SETTING: A tertiary university hospital. PARTICIPANTS: 202 patients undergoing elective cardiac surgery. INTERVENTIONS: Thromboelastometry was performed before cardiopulmonary bypass and 3 minutes after protamine administration. MEASUREMENTS AND MAIN RESULTS: The cohort study showed that the preoperative and postoperative thromboelastometric positive predicting value was poor (0%-22%); however, the negative predicting value was high (89%-94%). The systematic review of the literature to evaluate the predictive value of thromboelastometry for major postoperative bleeding in cardiac surgery resulted in 1,311 articles, 11 of which were eligible (n = 1,765; PubMed and Embase, until June 2016). Two studies found a good predictive value, whereas the other 9 studies showed a poor predictability for major postoperative bleeding after cardiac surgery. The overall negative predicting value was high. CONCLUSIONS: Thromboelastometry does not predict which patients are at risk for major postoperative bleeding.

Minimally Invasive Determinations of Oxygen Delivery and Consumption in Cardiac Surgery: An Observational Study.

OBJECTIVE: Evaluate minimally invasive assessment of oxygen delivery (DO2) and oxygen consumption (VO2) and determine its level of agreement with the gold standard approach of those measurements in patients undergoing cardiac surgery. DESIGN: Observational study. SETTING: Single center, VU University Medical Center (Amsterdam, The Netherlands). PARTICIPANTS: The study comprised 29 adult patients. INTERVENTION: Parallel measurements of invasive and minimally invasive parameters required for the calculation of DO2 and VO2. MEASUREMENTS AND MAIN RESULTS: Measurements were performed after anesthesia induction (T1) and before sternal closure (T2) in adult cardiac surgery. The invasive approach included arterial and pulmonary artery catheter-derived blood sampling and cardiac output measurements. The minimally invasive approach included pulse oximetry, point-of-care hemoglobin, Nexfin-based cardiac output, and central venous catheter-derived blood sampling. Level of agreement was determined using Bland-Altman analysis and percentage error. DO2 and VO2 levels were determined in patients 71 ± 8 years old. DO2 measurements showed a level of agreement of -17 ± 57 L/min/m2 and -18 ± 72 L/min/m2 with percentage errors of 35% and 38% at T1 and T2, respectively. VO2 assessment showed a level of agreement of -5 ± 18 L/min/m2 and -12 ± 22 L/min/m2, with percentage errors of 47% at T1 and T2. The highest percentage errors were for cardiac output measurements, 33% and 28% at T1 and T2, respectively. CONCLUSION: Agreement between minimally invasive and invasive DO2 and VO2 determinations is, moderate and poor, respectively. These findings may be explained by the poor agreement between minimally invasive and invasive cardiac output measurements.

Level of agreement between laboratory and point-of-care prothrombin time in patients after stopping or continuation of acenocoumarol anticoagulation: A comparison of diagnostic accuracy.

BACKGROUND: Procedures requiring optimisation of the coagulation status of patients using vitamin K antagonists are frequently postponed due to the late availability of laboratory international normalised ratio (INR) test results. A point-of-care (POC) alternative may facilitate early decision-making in peri-operative patients. OBJECTIVES: To assess the level of agreement between the POC-INR and the laboratory INR in patients who continue or stop vitamin K antagonists to determine whether the POC test may be a good alternative to the laboratory INR. DESIGN: Study of diagnostic accuracy. SETTING: Single-centre study at Zaans Medical Centre, The Netherlands. PATIENTS: Included patients were scheduled for cardioversion (these continued taking vitamin K antagonists), or a surgical procedure (these stopped taking vitamin K antagonists). MAIN OUTCOME MEASURES: The level of agreement and clinical acceptability of the laboratory and POC-INR results, evaluated by Bland-Altman analysis and error grid analysis. RESULTS: The surgical and cardioversion groups consisted of 47 and 46 patients, respectively. The bias in the INR in the surgical group was -0.12 ±â€Š0.09 with limits of agreement of -0.29 to 0.05, whereas the cardioversion group showed a bias in the INR of -0.22 ±â€Š0.36 with limits of agreement from -0.93 to 0.48. The percentage errors between methods in the surgical and cardioversion groups were 16 and 21%, respectively. Error grid analysis showed that the diagnostic accuracy of the POC prothrombin time is clinically acceptable as the difference did not lead to a different clinical decision in the surgical group with INR values less than 1.8. CONCLUSION: The current study shows a good level of agreement and clinical accuracy between the laboratory and POC-INR in patients who stopped anticoagulation intake for surgery. However, in patients who continued their anticoagulation therapy, the agreement between the two methods was less accurate.

Pulse-contour derived cardiac output measurements in morbid obesity: influence of actual, ideal and adjusted bodyweight.

The non-invasive Nexfin cardiac output (CO) monitor shows a low level of agreement with the gold standard thermodilution method in morbidly obese patients. Here we investigate whether this disagreement is related to excessive bodyweight, and can be improved when bodyweight derivatives are used instead. We performed offline analyses of cardiac output recordings of patient data previously used and partly published in an earlier study by our group. In 30 morbidly obese patients (BMI > 35 kg/m2) undergoing laparoscopic gastric bypass, cardiac output was simultaneously determined with PiCCO thermodilution and Nexfin pulse-contour method. We investigated if agreement of Nexfin-derived CO with thermodilution CO improved when ideal and adjusted-instead of actual- bodyweight were used as input to the Nexfin. Bodyweight correlated with the difference between Nexfin-derived and thermodilution-derived CO (r = -0.56; p = 0.001). Bland Altman analysis of agreement between Nexfin and thermodilution-derived CO revealed a bias of 0.4 ± 1.6 with limits of agreement (LOA) from -2.6 to 3.5 L min when actual bodyweight was used. Bias was -0.6 ± 1.4 and LOA ranged from -3.4 to 2.3 L min when ideal bodyweight was used. With adjusted bodyweight, bias improved to 0.04 ± 1.4 with LOA from -2.8 to 2.9 L min. Our study shows that agreement of the Nexfin-derived with invasive CO measurements in morbidly obese patients is influenced by body weight, suggesting that Nexfin CO measurements in patients with a BMI above 35 kg/m2 should be interpreted with caution. Using adjusted body weight in the Nexfin CO-trek algorithm reduced the bias.

Thermographic skin temperature measurement compared with cold sensation in predicting the efficacy and distribution of epidural anesthesia.

Due to the high rates of epidural failure (3-32%), novel techniques are required to objectively assess the successfulness of an epidural block. In this study we therefore investigated whether thermographic temperature measurements have a higher predictive value for a successful epidural block when compared to the cold sensation test as gold standard. Epidural anesthesia was induced in 61 patients undergoing elective abdominal, thoracic or orthopedic surgery. A thermographic picture was recorded at 5, 10 and 15 min following epidural anesthesia induction. After 15 min a cold sensation test was performed. Epidural anesthesia is associated with a decrease in skin temperature. Thermography predicts a successful epidural block with a sensitivity of 54% and a PPV of 92% and a specificity of 67% and a NPV of 17%. The cold sensation test shows a higher sensitivity and PPV than thermography (97 and 93%), but a lower specificity and NPV than thermography (25 and 50%). Thermographic temperature measurements can be used as an additional and objective method for the assessment of the effectiveness of an epidural block next to the cold sensation test, but have a low sensitivity and negative predictive value. The local decrease in temperature as observed in our study during epidural anesthesia is mainly attributed to a core-to-peripheral redistribution of body heat and vasodilation.